Reciclagem e balanço de fósforo a partir do uso de plantas de cobertura e fontes de adubação fosfatada em sistema de plantio direto

Abstract

Over the years, cover crops have been studied and categorized for their high capacity to restore the physical, chemical, and biological qualities of the soil, making them crucial for soil fertility in cropping systems. Consequently, phosphorus (P) in the soil—which is highly adsorbed by iron and aluminum oxides, binding strongly to colloids and becoming unavailable to plants—limits crop production, despite being a fundamental element responsible for energy formation and plant structures. Thus, since 2009, this experiment has sought to understand P dynamics and the effect of cover crops in a no-till system with corn and soybean cultivation. The objective is to demonstrate the importance of cover crops in recycling and maintaining P in the system over time, under the application of 100 kg of P₂O₅ via reactive rock phosphate and single superphosphate applied until 2015. In the 72 plots of a bifactorial fertilization experiment, the winter cover crops evaluated are: oats, forage radish, ryegrass, white lupin, rye, vetch, a MIX of oats, forage radish, and ryegrass, and fallow. Yield, cover crop dry matter production, and phosphorus balance based on extraction and export were evaluated. In the 2024/2025 harvest, average yields in the rock phosphate treatment with forage radish and rye reached values of 14,454 and 14,560 kg ha⁻¹, respectively. Dry matter production was also analyzed, reaching nearly 9,000 kg ha⁻¹ for white lupin under rock phosphate fertilization in 2024, and averages close to 7,000 kg ha⁻¹ of dry matter produced with rock phosphate for white lupin, oats, and the MIX. Furthermore, an equivalent phosphorus extraction/export efficiency was observed for the unfertilized treatment across almost all cover crops. It is possible to achieve high yields without the recurrent use of fertilization through the combination of cover crops and phosphorus sources with a higher persistence index in the system, such as rock phosphates, in addition to proving the efficiency of cover crops' chemical roles regarding nutrient cycling.